Furnace and means for controlling the draft therein



1,509,995 W. M. DUNCAN FURNACE AND MEANS FOR CONTROLLING THE DRAFT THEREIN Filed Fe 10 1921 5 Sheets-Sheet l [NI [N708 l I l I I I l l l ll llllln Se t. 30 1924.

Sept. 30 1924. 1,509,995

W. M. DUNCAN FURNACE AND MEANS FOR CONTROLLING THE DRAFT THEREIN Filed Feb. 10 192 3 Sheets-Shee't 2 g io JIM/[M7019 Y W fiwvaA/v Sept. 30, 1924. LSGELQQS w. M. DUNCAN FURNACE AND MEANS FOR CONTROLLING THE DRAFT THEREIN Filed Feb. 10 1921 3 Sheets-Sheet 5 Patented Sept. 30, 1924.

UNITED STATES WILLIAM M DUNCAN, OF ALTON, ILLINOIS.

FURNACE AND MEANS FOR CONTROLLING THE DRAFT THEREIN.

To all 'whom it may concern:

" Be it known that 1, WILLIAM M. DUNCAN, a citizen of the United States of America, and a resident of Alton, in the county of Madison and State of Illinois, have invented certain' new and useful Improve ments in Furnaces and Means for Controlling the Draft Therein, of which the followin is a full, clear, and exact description, reference being had to the accompanying drawings, forming a part of this specification. 1

This invention relates to improvements in furnaces and means for controlling the draft therein, and the novel features of the invention are adapted for use in a furnace provided with a traveling grate. The object of the invention is to prevent free escape of draft through openings in the bed of fuel supported on the grate.

It'is diificult to maintain a uniform bed of fuel on a grate, and this is especially true in a" furnace provided with a traveling grate. Actual experience has shown that an opening is sometimes formed in the fuel bed on a traveling grate, and the forced draft is then permitted to freely escape through the opening, with the result of very materially reducing the draft at other points in the fuel. The efficiency of the forced draft is thus very greatly reduced by the free escape of forced draft through an opening in the fuel which chills the combustible gases in the combustion chamber, and owing to this free escape, the draft will not be effective at other points of the fuel bed. I 4 According to the present invention, the -draft tending to pass to an opening in the fuel bed is retarded, or baffled, through the medium of draft-closures which do not prevent the transmission of draft through other portions of the fuel bed. These draft-closures may be constructed in any suitable manner and they may be provided with any suitable operating means.

In the particular apparatus herein shown, the draft-closures are in the form of small individual shields located below the fuel supporting portion of the grate and adapted to be adjusted transversely ofthe grate,

Application filed February 10, 1921. Serial No. 444,019.

so as to liebelow and form a closure for an opening in the fuel bed, thus preventing free escape of draft through said'opening. The several draft-closures may be adjusted successively so as to successively perform the function of closing an opening in the traveling fuel bed.

Fig. I is a longitudinal section, illustrat- I ing a mechanical stoker embodying the features of this invention, the middle portion of the apparatus being broken away.

' Fig. II is a transverse section of the structure shown in Fig. I. Fig; 111 is a diagrammatical top view showing the draft boxes and the draft closures which are adjustable along the upper portions of these boxes.

To illustrate the invention, I have shown a mechanical stoker comprising an endless chain grate A supported between side frame members 1 mounted on wheel s'2. The chain grate comprises many grate links 3 connected by means of pivot rods 1 arranged transversely of the grate. A power shaft 5 (Fig. I), supported by the side frames 1, is provided with any desired number of sprocket wheels 6 for transmitting movement to the endless chain grate. The chain grate passes around the sprocket wheels 6 and also around a plain idle wheel, or roll 7, the

latterbeing mounted on a shaft 8. The

fuel passes from a hopper 9 to the top face of the grate, as indicated by arrows in Fig. I.

The furnace is provided with suitable side walls B, including refractory members 10 located adjacent to the side margins of the grate. The lower portion of one of these side walls B is hollow, as shown in Fig. II, to provide an inlet passageway 11 for the draft. 12 designates draft boxes surrounded by the traveling grate and extending from a side frame 1 at one side of the grate to the frame lat the other side. All of these boxes are open at the top to provide for the delivery of the draft to the grate. Nipples 13 may be used to connect the respective draft boxes 12 to the draft passageway 11. Each draft box 12 may also be provided with a nipple 14: (Fig. II) for.

the discharge of ashes into a tubular memboxes, and the shields .oneof the shields is operative position at ber 15 provided with a normally closed door 16.

The several draft boxes 12 are located adjacent to each other, and they may be separated by members 17 (Fig. I) over which the grate links travel. 18 designates supporting bars located over the draft boxes 12 to form supports for the upper portion of the grate, and 19 designates similar bars located below and engaged by the lower portion of the traveling grate.

As an illustration of a suitable means for preventing free escape of draft through an opening in the fuel on the traveling grate, I have shown a succession of draft closures in the form of relatively small shields 20 adapted to pass through a side wall of the furnace (Fig. II) and also through a side frame 1. Guides 21, located at the upper margins of the draft boxes, are provided with grooves for the reception of the side margins of the shields 20. These guides 21 preferably extend from one of the side frames 1 'to the other side frame, so the shields 20 can be located at any desired points between the ends of the draft boxes. Each shield 20 is provider with an operating handle 22 located at the exterior of the furnace, and readily understood that the several shields 20 can be adjusted independently of each other.

.VVlien an opening is ing bed of fuel, oneof formed in the travel the shields 20 is adjusted to a position directly below the opening, and sincethe shield is located adjacent to thebottom of the fuel-supporting portion of the grate, the adjusted shield will prevent free escape of draft through the open ing in the fuel bed. However, the shield is so small that it will not prevent delivery ofthe draft to other portions of the fuel. As the bed of fuel travels away from the hopper 9, the portion of the fuel in which the opening is formed will be advanced so as to successively pass over the several draft 20 are adjusted sucthis opening. When withdrawn to an inone side of the grate, the next succeeding. shield is adjusted so as to lie directly below the course of that portion of the fuel. in which the opening is formed.

From the foregoing, it will be understood that the several shields aremovable transversely of the course of the traveling grate, so as to prevent free escape of draft through any predetermined point between the side cessively so as toclose margins of the grate.

a fuel-suppreventing draft through openings in grate, said means including it will be a series of draft-closures located between the grate and the source of the draft, said dra ftclosures being located below and movable transversely of the bottom of said grate so that either closure may be selected and located below an opening in the fuel and said draft-closures being shorter than the width of the grate so as to obstruct the draft tending to escape through said openin s and at the same time permit the delivery 0. draft through the fuel adjacent to said openings.

2. furnace provided with a traveling fuel-supporting grate, means for preventing free escape of draft through openings in the fuel on said traveling grate, said means including a succession of draft-closures located below and adjacent to the fuel-supporting portion of said traveling grate, said closures being interposed between the grate and the source of the draft and each of said closures being shorter than the width of the traveling grate, and means whereby said draft closures are movable trmisversely of the course of said traveling grate so as to prevent free escape of draft through any predetermined point between the SlCG margins of the grate where one of said closures may be located.

3. A furnace provided with a traveling free escape of draft through openings in the fuel on said traveling grate, said means including a draft-closure interposed between the traveling grate and the source of the draft and located below and adjacent to the fuel-supporting portion of the grate, said draft-closure being shorter than the width of the traveling grate, and means whereby said draft closure is adjustable transversely of the grate so as to form an obstruction for the draft at a predetermined middle portion. of the grate adjacent to which said draft-closure is located without obstructing the draft at the side margins of the grate.

1. A furnace provided with an endless traveling fuel-supporting grate, draft boxes arranged transversely of and surrounded by said endless traveling grate, said draft boxes being open at the top to provide for the delivery of draft through the upper portion of said endless traveling grate, and means for preventing free escape of draft through openings in the fuel supported on said traveling grate, said means including draft closures adjustable along the upper portions of thedraft boxes transversely of the course fuel-supporting grate. means for preventing of said traveling grate, each of said draftsuch length as to close small portion of the open to(p being ope 11 at the top to provide for the delivery of draft through the upper portion of said endless traveling grate, draft boxes being provided with each of said longitudi- 5 nal guides at its upper, margins, and relatlvely small draft-closures mounted in said guides, each of said draft-olosnres being adjustable along the top of one of said draft In testimony that I hereunto aifix my I claim the foregoing signature.

WILLIAM M. DUNCAN. 

